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ENTRAINMENT
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We’ll program our SLM
to follow a 14-minute
sequence that tracks the
meditation experience.
Since the device generates
only one frequency at a
time, it phases in new brain
states by switching fre-
quencies back and forth.
For example, to go from
fully awake to somewhat
dreamy, we generate beta
for a while, then alpha,
then toggle between
beta and alpha, reducing
the duration of beta and
increasing that of alpha
with each iteration. Our
code’s brainwave Tab array
defines the full sequence.
Brain entrains to the programmed wave sequence,
and alters its state accordingly.
Battery pack powers the electronics.
LEDs in front of user’s (closed) eyes pulse light at
2. 2, 6.0, 11. 1, or 14.4Hz, in order to elicit delta,
theta, alpha, or beta waves, respectively.
Headphone speakers play different tones into
right and left ears, to produce binaural beats (see
below) that match the LED pulse frequencies.
BINAURAL BEATS
Instead of simply playing the entraining wave
frequency through both headphone speakers, we
employ a more effective method. When we play
different frequencies into each ear, the brain
perceives a binaural beat frequency just as if the
two tones were played next to each other on
guitar strings. The beat results from the two
tones cyclically reinforcing and canceling each
other out, at a rate that equals the difference
between the frequencies.
To generate a beta binaural beat, we play a
400Hz tone in one ear and a 414.4Hz tone in the
other. The user perceives a sound, sort of like
“wah-oo-wah-oo-wah,” that fades in and out 14. 4
times per second.
Microcontroller on circuit board runs the
firmware, the program that resides in the
microcontroller, which controls the LEDs
and headphones.
Serial port connector writes the firmware into
the microcontroller, letting you program your
own brain wave frequency sequences.
Graphics simply look cool.
Wave 1 (red) and Wave 2 (blue)
Beat Pattern (green)
Make: 91
